Traditional composite floors are mostly based on polyvinyl chloride (PVC). However, a PVC-based floor has disadvantages in view of environment protection. For example, PVC-based floors may release toxic gases such as hydrogen chloride, carbon monoxide, and dioxin upon decomposition or combustion, and they usually contain phthalate plasticizers, which may produce reproductive toxicity when separated out. Moreover, PVC-based floors have poor dimensional stability.
Therefore, efforts have been made to look for an alternative composite floor material to replace PVC and some non-PVC-based floors have been developed. For example, Shaw Industries Group Corporation (Shaw) developed some non-PVC-based composite floors containing polyethylene, ethylene-propylene rubber and/or ethylene-butyl acrylate copolymer as substrate materials; Kangge Haslem Company (Congoleum) also developed some composite floors containing ethylene-methyl acrylate-acrylic acid terpolymer and/or ethylene-methyl acrylate copolymer as substrate materials.
CN102277945A discloses a non-PVC-based composite floor containing polyethylene, ethylene-propylene rubber and/or ethylene-butyl acrylate copolymer as the substrate layer, which solved the environmental problem and plasticizer separating-out problem of a PVC-based floor. The structure of the composite floor comprises, from top to bottom, a wear-resistant layer, a connective layer, a decorative layer, optionally another connective layer, a primary substrate layer, and a secondary substrate layer. However, this patent application document does not disclose how to solve the following problems that may be present in this kind of non-PVC composite floors:                (A) poor transparency of the wear-resistant layer;        (B) poor dimensional stability of the floor;        (C) poor scratch-resistance of the surface of the floor;        (D) poor compactness between the floor and the ground;        (E) poor compactness between the wear-resistant layer and the decorative layer;        (F) poor compactness between the decorative layer and the substrate layer; and        (G) using an extrusion process or multilayer co-extrusion process or casting process, which has low production capacity & production efficiency, and the product cost is considerably high.        
Accordingly, there has been a need to find better structural materials for non-PVC-based composite floors and their preparation processes in order to overcome the deficiencies of the prior art and to obtain an ideal composite floor.